While I have been clear that I am skeptical of the attempts to tie the Islamic State to Iraqi Ba‘athism and what I see as an overemphasis on the importance of former Iraqi Ba‘athists/Saddam-era security personnel within the Islamic State, there are nonetheless some notable cases of Saddam-era security personnel who became involved in the Islamic State.
In an even more interesting story, we have the case of a half-nephew of Saddam who became an Islamic State commander. This person is Ibrahim bin Sab‘awi, whose biography was recently documented by a pro-Islamic State writer who appears to be based out of Iraq. Ibrahim was killed in fighting in the Bayji area in northern Iraq in 2015 (the Bayji area was a site of heavy fighting for an extended period between the Islamic State and Iraqi forces). He also notably participated in the Speicher massacre of June 2014, in which the Islamic State deliberately targeted Shi‘a cadets in an act of mass execution.
The biography is translated below.